Yus Miguel, Herrera Raquel P, Guijarro Albert
Departamento de Química Orgánica Facultad de Ciencias Universidad de Alicante, Apdo. 99, 03080 Alicante, Spain.
Chemistry. 2002 Jun 3;8(11):2574-84. doi: 10.1002/1521-3765(20020603)8:11<2574::AID-CHEM2574>3.0.CO;2-K.
The use of lithium and a catalytic amount of an arene is a well-established methodology for the preparation of organolithium reagents that manifest greater reactivity than the classical lithium-arene solutions. In order to rationalize this conduct, the participation of a highly reduced species, the dianion, is proposed and its reactivity explored. Studies of kinetics and of distribution of products reveal that the electron-transfer (ET) reactivity profile of dilithium naphthalenide in its reaction with organic chlorides excludes alternative mechanisms of halogen-lithium exchange. The process generates organolithium compounds. The dianion thus emerges along with the radical anion as a suitable candidate for catalytic cycles in certain processes. Endowed with a higher redox potential than its radical anion counterpart, dilithium naphthalene displays a broader spectrum of reactivity and so increases the range of substrates suitable for lithiation. The reaction of dilithium naphthalene with THF is one example of the divergent reactivity of the radical anion and the dianion, which has been the source of apparent misinterpretation of results in the past and has now been appropriately addressed.
使用锂和催化量的芳烃是制备有机锂试剂的一种成熟方法，这些有机锂试剂表现出比经典的锂 - 芳烃溶液更高的反应活性。为了合理解释这种行为，有人提出了一种高度还原的物种——双负离子的参与，并对其反应活性进行了探索。动力学和产物分布研究表明，萘锂双负离子与有机氯化物反应的电子转移（ET）反应活性概况排除了卤素 - 锂交换的其他机制。该过程生成有机锂化合物。因此，双负离子与自由基负离子一起成为某些过程中催化循环的合适候选者。萘锂双负离子具有比其自由基负离子对应物更高的氧化还原电位，表现出更广泛的反应活性，从而增加了适合锂化的底物范围。萘锂双负离子与四氢呋喃的反应是自由基负离子和双负离子不同反应活性的一个例子，这在过去一直是导致结果明显误解的根源，现在已经得到了恰当的解决。
